Hot-gas reciprocating engine



Dec. 13, 1960 R. J. MEIJER HOT-GAS RECIPROCATING ENGINE 2 Sheets-Sheet 1 Filed March 9, 1959 I'NVENTOR ROELF JAN MtlJER flJ f AGE Dec. 13, 1960 R. J. MEIJER HOT-GAS RECIPROCATING ENGINE 2 Sheets-Sheet 2 Filed March 9, 1959 INVENTOR ROELF JAN MEIJER United States Patent HOT-GAS RECIPROCATING ENGINE Roelf Jan Meijer, Eindhoven, Netherlands, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed Mar. 9, 1959, Ser. No. 798,140

Claims priority, application Netherlands Mar. 28, 1958 2 Claims. (Cl. 60-24) This invention relates to hot-gas reciprocating engines of the displacer type. It is known for such engines, which are to be understood to mean both hot-gas reciprocating motors, cold-gas refrigerators and heat pumps, the last-mentioned two engines operating on the reverse hot-gas motor principle, to be designed so that such an engine comprises two identical cranks located on each side of a plane passing through the centre line of the engine, which cranks form parts of two relatively synchronous crank shafts which rotate with the same phase and in opposite senses and are provided with counterweights, the centre lines of said crank shafts being located parallel and symmetrically on each side of said plane through the centre line of the engine in a plane at right angles to the plane passing through the centre line of the engine, the couplings between the piston and the displacer and the cranks on the crank shafts each including a piston driving rod or a displacer driving rod. The piston driving rods are of equal length and so are the displacer driving rods. The parts of the piston driving rods moving rectilinearly are located on one side of the plane passing through the centre lines of the crank shafts, and the correspondingly moving parts of the displacer driving rods are located on the other side thereof, and in each half of the engine located on one side of a plane passing through the centre line of the cylinder, one of the driving rods present there has two pivots and a centre of rotation, the latter applying to the crank, whereas the other driving rod has only two pivots, the first-mentioned driving rod being coupled at its rectilinearly moving pivot to the piston or the displacer, whereas the second pivot of this driving rod co-acts with one pivot of the driving rods having two pivots, of which the other pivot, likewise moving rectilinearly, is coupled to the displacer or the piston.

In an engine of the kind described above, the required phase difference between the movement of the displacer and the movement of the piston is obtained in a simple manner. Furthermore, the engine may be balanced relatively very well.

In this known engine, it would be necessary for obtaining complete balancing that the two driving rods each have a centre of rotation by means of which they can rotate about the same crank. This embodiment has structural disadvantages, so that in the known engine one driving rod has two pivots and a centre of rotation and the other driving rod has two pivots, the driving rods being coupled together at one pivot and hence only one driving rod applying to the crank of the engine. However, complete balancing cannot be obtained with this structurally attractive embodiment and with the specified dimensions of the driving rods.

It has been found that the possibility of complete balancing can nevertheless be obtained also in the structurally simple embodiment of known type, it, according to the invention, certain proportioning descriptions are followed.

The engine according to the invention is characterized ice in that the distances between the pivots present on each driving rod are equal and that furthermore there applies the relationship:

in which m is the mass concentrated at the point where the pivot of the driving rod having two pivots and one centre of rotation is coupled to the piston or the displacer and consisting of half the mass of the piston, the displacer and respectively of the piston rod or displacer rod when present, with the associated coupling mechanism, together with that portion of the mass of the driving rod which is obtained if this mass is divided over the centre of rotation and the pivots in accordance with the lever rule;

m =the mass concentrated at the point where the pivot of the driving rod having only two pivots is coupled to the displacer or the piston and consisting of half the mass of the displacer or the piston and of the displacer rod or piston rod when present with the associated coupling mechanism, together with that portion of the mass of the driving rod which is obtained if this mass is divided over the pivots in accordance with the lever rule;

m =the mass concentrated at the common pivot of the two driving rods and consisting of the portion of the mass of the driving rod having two pivots and a centre of rotation and the portion of the mass of the driving rod having only two pivots, both portions ob tained in accordance with the rule given with m; and m.,;

7\=the radius of the crank, divided by the distance between the centre of rotation and the pivot associated with the same driving rod, which pivot is coupled to the piston or the displacer, the radius of the crank being assumed to be equal to unity;

v=the distance between the centre of rotation and the pivot associated with the same driving rod, to which the pivot of the second driving rod is coupled, divided by the radius of the crank, the latter assumed to be equal to unity, and

=the angle which in the case of the driving rod having two pivots and a centre of rotation, is enclosed between the lines connecting each pivot and the centre of rotation.

In one embodiment of the invention, the angle 13 satisfies the equation:

in which the mass m of this counterweight which is concentrated at the centre of gravity of the counter weight is equal to In the above equations w=the angle which, if the centre of rotation lies on that side of the plane through the crank shafts which is opposite to the side where the pivot of the driving rod having two pivots and a centre of rotation coupled to the piston or the displacer is present and the radius of the crank is at right angles to said plane, is enclosed between this radius of the crank and the line connecting the centre of gravity of the counter-weight and the centre line of the crank shaft, as measured from the radius of the crank in a direction which, at least initially, extends from the centre line of the engine;

m =the mass concentrated at the centre of rotation and consisting of the portion of the mass of the driving-rod part of the driving rod having two pivots and a centre of rotation, obtained in accordance with the lever rule;

m =is the mass of the crank concentrated at the centre of gravity thereof;

p =the relative distancebetween the centre of the crank shaft and the centre of gravity of the counterweight or the distance between the centre-of the'crankshaft and the-center of gravity of the counterweight divided by the distance between the centre of the crankshaft and the centre of the crank.

The term lever rule is to be understood, as usually, to mean the rule according to which the algebraic sum of the masses concentrated in the said points and multiplied by their lever arms, that is to say, in this casethe distances between the points and two arbitrary lines passing through the centre of gravity and located in the same plane as the points projected in this plane, is zero with respect to said lines.

In order that the invention may be readily carried into eifect, several embodiments will now be explained in detail, by way of example, with reference to the accompanying drawings, in which:

Fig.1 is across-sectional view of a hot-gas reciprocating engine of the displacer type;

Fig. '2 shows a driving rod having two pivots and a centre of rotation, with masses concentrated at these points and suspended in a pivot, which-figure serves to explain the term lever rule;

Fig. 3 shows the driving rod of Fig. 2, but now suspended in another pivot;

Figs. 4, 5, 6 and 7 show diagrammatically four different embodiments of-the driving mechanism.

Referring now to Fig. 1, reference numeral 1 indicates a cylinder of a hot-gas reciprocating engine in which a displacer 2 and a piston 3 are adapted to reciprocate. The upper end of the cylinder is constituted by acylinder head 4 which has internal fins 5 and external fins 6. A lining 7 separates the fins 5 and a regenerator 8-from the interior of the cylinder. The cylinder also has bores 9 which communicate with a space containing fins-10 secured to a body 11 which has exter nal ribs 12, the fins and the ribs constituting the cooling system. The cylinder head 4 is surrounded by a body 13 containing a burner 14 (shown diagrammatically). The combustion gases pass along the fins 6, leaving the body 13, after having dissipated-their heat, through an outlet channel 15. The cylinder head 4 is secured by means of bolts 16 to the body 11, which is secured likewise by means of bolts 17 to a crank case 18. By means of'said bolts, the cylinder 1 is also rigidly joined to the crank case 18. The piston 3 has a hollow piston rod 19. Two heads 21 of two driving rods 22 can swing about a shaft 20, which is rigidly secured'to the pistonrod 19, a displacer rod23 which is rigidly secured to the displacer being led through the piston rod 19 and the shaft 20. The driving rods 22 also have two centres of rotation 24,which can rotate about crank pins 25. Ball bearings are provided between the centres of rotation 24 and the crank pins 25. Rigidly secured to the centres of rotation 24 are plates 26, provided with pins 27 about which two heads 28 of displacer driving rods can swing. At the other ends of the displacer driving rods 29 there are provided heads 30 which each can swing about a shaft31 whichis rigidly secured to displacer rod'23. The crank pins 25 are provided eccentrically on shafts 32, which are coupled together by means of gear wheels 33 and on which counter-weights35 are arranged by'mea'ns 'ofscrews 34. The crank case 18 is 4 closed by means of a cover 36 so that the whole crank case may be filled with oil, if desired.

The distance between the pivot 20 and the pivot 27 is exactly the same for the two piston driving rods and also exactly equal to the distance between the pivots 31 and 27 of the displacer drivingrods; the angle (p enclosed between the lines 2725 and 25-20, the weight of the counter-weight 35 and the angle 7 enclosed between the connecting line 2725 and the line connecting the centre of gravity of the counter-weight 35 and the centre of the crank shaft 25 are determined in accordance with the equations specified hereinafter.

Figs. 2 and 3 show a driving rod 50 having a centre of rotation at T and pivots at points Z and S. The centre of rotation T is connected to the crank; the pivots Z and S are imagined to be connected to the piston and to the displacer respectively. It will be evident that the three masses m m and m which are imagined to be concentrated at the points Z, T and S, may readily be determined since the rod, if suspended at Z, is at rest, if the algebraic sum of'the moments m a and m xa with respect to the'perpendicular through Z is zero and such is the case in'Fig. 3, if m a =m a in-which the rod is suspended at S. Furthermore, m +m +m must be equal to the whole mass of the rod 50. I

Figs. 4, 5, 6 and 7 show diagrammatically four different embodiments of driving rods, it being assumed that'the piston rod is connected to point Z and the displacer rod is connected to point Y. The centre line of the crank shaft is indicated by 0 and the crank pin bears the character T. Connected to the crank pin T is a driving rod 101, of which the second pivot, to which the displacer driving rod is coupled, is indicated by S. The distance between the centre of rotation T and the pivot S is v, and the angle enclosed between ZT and TS is (p The centre of gravity of the counter-weight bears the character W and the relative distance between W and O is indicated by p Similarly, K is the centre of gravity of the crank and p is the relative distance between K and 0 The angle enclosed between W0 and K0 is 7 The masses m m m m m and m are imagined to be concentrated at the points Z, T, S, V, W and K. The length of the portion TZ of the driving rod is assumed to be equal to being the ratio between the distance O T divided by the distance T2. The radius O T of the crank is regardedas a unit and assumed to be equal to unity. It canthen readily be recognizedthat, according to the cosine rule,

According to the invention, the distance SV is equal to the distance ZS. The masses m and m; of the masses m m m m m and m consist of half the masses of the pistonand the displacer and possibly of the piston rod and the displacer rod with the associated coupling mechanism, together with the weight of the driving-rod portion determined in accordance with the lever rule; m is the sum of the weights of the driving rods after the allocation in m m and m m is the mass of the rod 101 concentrated at the centre of rotation in accordance with the lever rule; m is the mass of the counter-weight concentrated at the centre of gravity W, and m is the mass of the crank concentrated at the centre ofgravity K thereof. The mass m is determined by the equation wherein p is the relative distance 'from 0 to W and pg is the distance from O to K.

3 Lastly, the angle between W and 0 K, as indicated by 7 is determined by The driving rod 2ST, indicated by 101, has difierent shapes in Figs. 4, 5, 6 and 7. In Figs. 4 and 6, the rod is bent and in Figs. 5 and 7 it is rectilinear. Furthermore, in Figs. 4 and 7, the centre of rotation lies between two pivots, but in the case of the rod shown in Figs. 5 and 6, the centre of rotation lies at the end of the rod. Correspondingly, the angle (p also has a different shape, (p being acute in Fig. 4, but 0 in Fig. 5. In Fig. 7, p has a value of 180. However, in Fig. 6, (p is again an acute angle 4ZTS.

What is claimed is:

1. In a hot-gas reciprocating engine comprising a cylinder, a displacer within said cylinder, a piston within said cylinder and provided with a bore extending axially of the cylinder, means connecting said piston and displacer in an out-of-phase relationship, said means including counterweights comprising two members rotatably mounted on axes located one on each side of the axis of the cylinder, a pivot located eccentrically on each of said members, two piston connecting rods of equal length each having one end pivotally connected to said piston, two elongated crank members each rotatably mounted on one of said pivots, the free end of each of said piston connecting rods being pivotally secured to each adjacent crank member, a displacer rod having one end operatively connected to said displacer and extending through the bore of said piston, two displacer connecting rods of equal length, each having one end rotatably secured to the free end of said displacer rod and means pivotally securing the other end of each of said displacer connecting rods to one of said crank members at a point spaced from the adjacent pivot, each of the piston connecting rods having substantially the same length as each displacer connecting rod; the combination in which one of said connecting rods has two articulated pivots and a center of rotation about one of said crank members and another of said connecting rods has two articulated pivots only, said one connecting rod being coupled with its linearly moving pivot to said piston or said displacer while said other connecting rod coacts at one end with the second pivot of said one connecting rod, and a linearly moving pivot at the other end of said other connecting rod being connected to said displacer or said piston, the distance between the two pivots on each of said piston and displacer connecting rods being equal and for each half of said engine lying on one side of the said longitudinal plane of symmetry the following relationship applies:

m m +7\v(m |2m COS 0o=0 and that the angle 7 is equal to 11(71'14; sin $0 whereas the mass m of the counter-weight, concentrated in the center of gravity of the counter-weight, is equal to:

in which relations:

m =the portion of the mass of the connecting rod having two pivots and one centre of rotation, that is obtained, when the mass of this connecting rod is divided between the center of rotation and the two pivots in accordance with the lever rule and which is imagined to be concentrated in that pivot of this connecting rod, which is coupled, possibly by means of a coupling mechanism and/ or a rod, to the piston or the displacer increased by half the mass of this piston or this displacer; and this coupling mechanism and/or rod;

m =the portion of the mass of the connecting rod having two pivots and a'center of rotation, obtained in accordance with the lever rule, which is imagined to be concentrated in the center of rotation;

m =the portion of the mass of the connecting rod having two pivots and one center of rotation, increased by the portion of the mass of the connecting rod having only two pivots, both portions obtained by the lever rule and imagined to be concentrated in the common pivot of the two connecting rods;

m =the portion of the mass of the connecting rod having two pivots that is obtained, when the mass of this connecting rod is divided between the two pivots in accordance with the lever rule and which is imagined to be concentrated in that pivot of this connecting rod, which is coupled, possibly by means of a coupling mechanism and/ or a rod, to the displacer or the piston, increased by half the mass of this displacer or this piston and of the coupling mechanism and/or the rod when present;

m =the mass of the crank, which is imagined to be concentrated at the center of gravity thereof;

p =th6 relative distance between the center of the crank shaft and the center of gravity of the counter-weight with respect to the radius of the crank =r /r;

p =th6 relative distance between the center of the crank shaft and the center of gravity of the crank pin with respect to the radius of the crank =r /r;

\=the radius of the crank divided by the distance between the center of rotation of the connecting rod having a center of rotation and two pivots and the pivot of this connecting rod, which pivot is coupled to the piston or the displacer;

v=the distance between the center of rotation of the connecting rod having a center of rotation and two pivots and the pivot of this connecting rod, to which the pivot of the second connecting rod is connected, divided by the radius of the crank;

=the angle which, in the case of the connecting rod having two pivots and a center of rotation, is included between the lines connecting each pivot with the center of rotation;

7 =the angle which, if the center of rotation and measured from the line which connects the center of rotation with the pivot, is connected to the piston or displacer towards the longitudinal plane of symmetry of the engine lies on that side of the plane through the axis of rotation of the crank shafts which is opposite to the side where the pivot of the driving rod having two pivots and a center of rotation connected to the piston or displacer is present and the radius of the crank is at right angles to this plane, is enclosed between this radius of the crank and the line connecting the center of gravity of the counter-weight and the axis of rotation of the crank shaft, as measured from the radius of the crank in a direction which, at least intially, extends from the longitudinal plane of symmetry of the engine.

2. In a hot-gas reciprocating engine of the displacer type comprising a cylinder, a displacer within said cylinder, a piston within said cylinder and provided with a bore extending axially of the cylinder, means connecting said piston and displacer in an out-of-phase relationship and having two identical cranks located on each side of a plane of symmetry passing through the longitudinal center line of the engine, two crankshafts, said cranks being part of said two crank shafts and adapted to rotate synchronously with equal phases and in opposite directions, said cranks being provided with counterweights, the axes of rotation of said crankshafts being located parallel and symmetrically on each side of said plane of symmetry of the engine, said means including piston connecting rods and displacer connecting rods, the piston connectlng rods being of equal length while the displacer connecting rods are also of equal length, and the rectilinearly moving-parts of the piston connecting rods being situated on one side of the'plane in which the axes of rotation-of said crankshafts are located and the correspondingly moving parts of the displacer connecting rods being located on the other side of said plane; the combination in each half of the'engine located on one side of said plane'of symmetry in which combination one of said connecting rods'has two articulated pivots and a center of rotation about one of said cranks and another of 'said' connecting rods has two articulated pivots only, said one connecting rod being coupled with its linearly moving pivot to said piston or said displacer while said other connecting rod coacts at one end with the second pivot of said one connectingrod, and a linearly moving pivot at the outer end of said other connecting rod being connected to saidtdisplacer or said-piston, the distance between the two pivots on each of said piston and displacer connecting rods being equal and for each said half of the engine lying on one side of the said longitudinal planeof symmetry, the following relationship applies:

whereas the mass m of the counter-weight, concentrated in the center of gravity of the counter-weight, is equal to:

- arctan inwhich relations:

m =the portion of the mass of the connecting rod having two pivots and one centre of rotation, that'is obtained, when the mass'of this connecting rod is divided between the center of rotation and'the two pivots in accordance with the lever rule and which is imagined to be concentrated in that pivot of this connecting rod, which is coupled, possibly by means of a coupling mechanism and/or a rod, to the piston or the displacer increased by half the mass of this piston or this displacer; and this coupling mechanism and/ or rod;

m =the portion of the'massof the connecting rod having twopivots and a center of rotation, obtained in accordance with the lever rule, which is imagined to be concentrated in the center ofrotation;

m3=the portion of the mass of the connecting rod having two pivots and one center of'rotation, increased by the portion of the mass of the connecting rod having only two pivots, both portions obtained by the lever rule and-imagined to be concentrated in the common pivot of the two connecting rods;

m ,=the portion of the mass of the connecting rod having two pivots that is obtained, when the mass of this'connecting rod is divided between the'twopivots'in accordance withlthel'ever rule and which is imagined to be concentrated in that pivot of this connecting rod, which is coupled, possibly by means of a coupling mechanism and/or'a rodfto the displacer or the piston and of the coupling mechanism and/or the nod when present; v

mg=the mass of the crank; which is imagined to be concentrated at the center of gravity thereof;

=there1ative distance between the center of the crank shaft and'the center of gravity of the counter-weight with respect to the radius of the crank =r r;

=the relative distance between the center of'the crank shaft and the center of gravity ofthe crank pin with respect to the radius of the crank ='r /r;

A=the radiiis o-f'the crank divided by the distance between the center of rotation of'the connecting rod havingaeemer of rotation and two pivots and the pivot of this connecting rod, which-pivot is coupled to the piston or the displacer;

v=the distance between the center of rotation of the connecting rod'havi'n'ga center of rotation and two pivots 'and the pivot of this connectingrod, to which the pivot of the secondcconnecting rod is connected, divided by the radius of the crank;

5=the angle which, in-the case-of the connecting rod having two pivots and a center of rotation, is included betweenthe lines connecting each pivot withthe center of rotation and measured from the line, which connects the center of rotation with the pivot, which is connected to the piston or di'splacer, towards the longitudinal plane of symmetry of the engine;

=the angle which, if the center ofrotation lies on that side of the plane throughthe axis of rotation of the crank shafts whichis opposite to the side where the pivot of the driving rod having two pivots and a center of rotation connected to the piston or displacer is present and the radius of the crankis at right angles to this plane, is enclosed between this radius of the crank and the line connecting the center of gravity of the counterweight and the axis of rotation of the crank shaft, as measured from the radius 'of the crank in a direction which, at least initially, extends'from the longitudinal plane of symmetry of the engine.

References Cited in the file of this patent UNlTED STATES PATENTS 1,701,439 Canfield Feb. 5, 1929 2,392,921 Holman Jan. 15, 1946 2,885,855 Meyer May 12, 1959 

